This invention relates to methods and apparatus for coupling two single rows of continuous elements for a slide fastener into a double element row and more particularly to a method and apparatus for coupling two single element rows which have been discharged respectively from a pair of separately located element shaping and transporting machines having different power sources, said method and apparatus giving a constant tension to the rows of elements and controlling the speeds of both of discharge of the respective single element rows and of withdrawal of the combined or double element row.
In the production of a pair of fastener stringers each carrying on and along its one longitudinal edge a row of continuous fastener elements, it has been customary to mesh together the respective rows of fastener elements and thereafter secure them to the respective tapes by means for example of sewing operation. It is therefore necessary to provide a procedure whereby the two single rows of continuous fastener elements are coupled together prior to attachment to the carrier tapes. This procedure is desirable from the viewpoint of preventing such continuous fastener elements as in a meandering or a coil form from getting entangled or twisted due to deformation of the elements which would otherwise take place when the element rows are stored unpaired for extended periods of time.
One prior attempt to intermesh the two rows of continuous fastener elements was to use a single machine in which are provided in symmetric relation two separate element forming apparatus driven by a common power source and which is therefore capable of producing a pair of rows of continuous fastener elements at a synchronous rate of speed so that the respective element rows discharged can be readily coupled together. However, such prior art machines would become considerably large in size and require increased power to keep its operation. They were furthermore inconvenient to manipulate and difficult to dismount, assemble or service because the two apparatus had to be located remotely in parallel.
Another prior art attempt was to intermesh the rows of fastener elements which have been continuously discharged in opposite direction from a pair of separately located element forming machines driven by different sources of power. However, it was very difficult to equalize the number of revolutions of one of the two power sources accurately with that of the other, with the results that the rates of discharge speed of the two single element rows would become different one from the other and furthermore the tension applied to one row of elements would accordingly vary relative to that applied to the other element row.